Calories and Body Fat – The Basics

A calorie is a unit of energy. The estimated average daily calorie requirement is 2000 for women and 2500 for men, this is just an estimate and will depend on your age, weight, height, body composition and levels of activity.

Calories are not only used up when you exercise there are 3 components to the way your body uses the calories (energy) you put in it:

1. Basal Metabolic Rate

Your body burns 60-70% of energy just by functioning – this is known as the Basal Metabolic Rate (BMR) and is the energy expended by the functioning of your vital organs such as your heart, kidneys, liver, intestine, nervous system, skin, muscles, lungs etc. So this can be thought of in terms as using energy for activities such as breathing, heart beat, regulating your body‘s temperature etc.

2. Thermic Effect of Food

Digesting your food also uses up calories, this is called the Thermic Effect of Food (TEF). This accounts for approx 10% of your calories used, although it can differ greatly depending on the type of food you are eating, protein for instance is harder to process than dietary fat so digesting protein will use up more calories than digesting the fat.

3. Physical Activity

Physical activity accounts for 20-30 % of energy your body uses. Everything that you do during your day will be using up calories, brushing your teeth, making your bed, having a shower etc. Depending on how much activity you do during your day will depend on how many calories your body uses.

This is why it is important that you get the correct amount of calories each day so that your body can function normally and complete everything you ask of it in terms of physical activity and that is also why the amount of calories you need to consume can also differ eg. if you are an athlete and training for 3-4 hours per day you will need more calories than someone who sits at a desk in an office all day.

How many calories are you eating?

When wanting to lose weight a good idea is to work out how many calories per day you actually consume. Keep a food diary for 7 days, every time you eat or drink something put it in your diary each day, make sure it is a typical week for you (be honest with yourself and don‘t try to watch what you eat just because you are writing it down as it defeats the purpose of finding out what you would normally consume in a typical week). Make sure you remember to list everything whether it was half a biscuit or a half a cup of orange juice, add everything and how much of it you consumed.

Once you have a completed week add all your calories up and divide by 7, that will give you your average daily calorie intake. Compare that to the estimated average daily calorie requirement figures (2000 for women and 2500 for men). If you are exceeding these then you need to cut down on the calories you are consuming as any calories you take in over what you need/use during your week will be stored as fat.

Lose body fat not weight

To lose weight you want to look at losing fat more than just losing weight, this is because you can lose weight on the scales but you may not be losing only fat, depending on how you are exercising to lose the weight you may be losing lean muscle mass as well. When people normally say they want to lose weight it is normally the fat that we want gone.

To determine how much weight you should lose it is a good idea to have your body fat % measured. You can then use the figure to work out how much of your weight is fat and how much is lean tissue. You can then decide your body fat % goal and work out how much weight (body fat) you need to lose.

This table shows the different categories when measuring body fat %.

Classification

Women
Fat %

Men
Fat %

Essential

10-13 %

2-5 %

Athlete

14-20 %

6-13 %

Fitness

21-24 %

14-17 %

Average

25-31 %

18-24 %

Obese

32% and higher

25% and hgher

As you will see there is a category for essential body fat but it is receommended that your minimum total body fat % exceeds this figure. This is becasue you not only need essential fat but some storage fat as well. The essential fat is needed for your body to function and the storage fat is what helps protect your organs.

How many calories to lose weight?

So now you want to start losing the fat you need to know how many calories you should be aiming to burn off. A healthy and realistic amount of weight to lose is 1lb per week. 1lb of fat is approx 3500 calories, so if you wanted to lose 1lb per week you would need to create a 500 calorie deficit per day. So that’s 3500 calories per week. Simple.

Remember that to lose weight you need to exercise and have a healthy and balanced diet. Don’t just reduce your calorie intake to lose the weight because this can have the opposite affect. This is why diets sometimes don’t work, it may look like the diet is working and you see weight come off but as soon as you start to eat normally again your will just put the weight straight back on and it wont take long either. If your body does not have enough fuel it will go into starvation mode, once it has burnt the fat reserves it will then start to use lean tissue and muscle this is what is know as starvation mode and is not something you want your body to do so make sure you eat a healthy balanced diet. That way you will lose weight and be able to keep it off.

The changes you make need to be lifestyle changes, they need to be ones that you can stay with for the rest of your life so choose a healthy active lifestyle.